package org.apache.lucene.index;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.File;
import java.io.FilenameFilter;
import java.util.HashSet;

/**
 * Filename filter that accept filenames and extensions only created by Lucene.
 *
 * @lucene.internal
 */
public class IndexFileNameFilter implements FilenameFilter {

    private static IndexFileNameFilter singleton = new IndexFileNameFilter();
    private HashSet<String> extensions;
    private HashSet<String> extensionsInCFS;

    // Prevent instantiation.
    private IndexFileNameFilter() {
        extensions = new HashSet<String>();
        for (String ext : IndexFileNames.INDEX_EXTENSIONS) {
            extensions.add(ext);
        }
        extensionsInCFS = new HashSet<String>();
        for (String ext : IndexFileNames.INDEX_EXTENSIONS_IN_COMPOUND_FILE) {
            extensionsInCFS.add(ext);
        }
    }

    /* (non-Javadoc)
     * @see java.io.FilenameFilter#accept(java.io.File, java.lang.String)
     */
    public boolean accept(File dir, String name) {
        int i = name.lastIndexOf('.');
        if (i != -1) {
            String extension = name.substring(1 + i);
            if (extensions.contains(extension)) {
                return true;
            } else if (extension.startsWith("f") && extension.matches("f\\d+")) {
                return true;
            } else if (extension.startsWith("s") && extension.matches("s\\d+")) {
                return true;
            }
        } else {
            if (name.equals(IndexFileNames.DELETABLE))
                return true;
            else if (name.startsWith(IndexFileNames.SEGMENTS))
                return true;
        }
        return false;
    }

    /**
     * Returns true if this is a file that would be contained
     * in a CFS file.  This function should only be called on
     * files that pass the above "accept" (ie, are already
     * known to be a Lucene index file).
     */
    public boolean isCFSFile(String name) {
        int i = name.lastIndexOf('.');
        if (i != -1) {
            String extension = name.substring(1 + i);
            if (extensionsInCFS.contains(extension)) {
                return true;
            }
            if (extension.startsWith("f") && extension.matches("f\\d+")) {
                return true;
            }
        }
        return false;
    }

    public static IndexFileNameFilter getFilter() {
        return singleton;
    }
}
